A standard sieve has a generally horizontal mesh, which term here is intended to cover any perforated sheet whether woven or not, whose ends at least are fixed to a frame that is reciprocated with at least some horizontal component. Thus particulate material placed on the mesh will be bounced about and those particles smaller than the mesh openings will fall through.
In order to maximize movement of the particulate material being graded it is known from German patent document 1,206,372 filed Sep. 26, 1964 by A. Wehner to fix the mesh to a plurality of horizontal and parallel bars each fixed to one of two frames with every other bar secured to the same frame. A drive is connected to and between the two frames to move them oppositely so that the mesh surface is subdivided into a plurality of different panels that move alternately, with half of the panels being pulled taut while the others are becoming slack and vice versa. Such a system is fairly complicated to build and its drive is quite expensive. Furthermore it is impossible to retrofit this system to an existing sieve whose mesh is held in a single panel that is moved all together.
It has been suggested to somehow mount some support elements of the mesh independently so that they do not have to be independently driven, but no practical system has been made. Such an arrangement has been proposed in combination with a system having removable mesh panels but, once again, no practical realization is known.